The present invention is directed to optical devices such as those used for night vision.
Portable night vision devices are widely used in the military and in law enforcement operations to provide personnel with the ability to view objects at night or during other low light conditions. These devices generally include an objective lens assembly, an image intensifier tube, and an eyepiece, and typically are physically embodied in the form of a monocular device which attaches to a helmet or headband.
By way of background, a monocular device, as the name implies, has a single optical channel giving an intensified view of the low light level scene to one eye. A biocular device presents the same view to both eyes by means of a dual channel eyepiece. A binocular device, on the other hand, has two monocular channels fixed together to present a slightly different view to each eye. Binocular vision provides improved depth perception, and there are some night operational missions, including driving land vehicles or boats, where depth perception helps with the judgment of distances.
The most widely fielded portable night vision devices are in monocular form. It would be desirable to be able to take two monocular devices and quickly assemble a binocular device for those applications where depth perception is necessary. Any such device must have a means for allowing adjustment of the distance between the monoculars, known as the interpupillary distance, to allow for the variation in the distance between the eye pupils of different human beings.
A binocular night vision device needs to have the two intensified images of an object collimated in image space such that the object is presented to each of the user""s eyes at the same azimuth and elevation in the binocular field of view. The two pictures are combined in the brain to give binocular vision in the same way as such vision is achieved in normal, unaided daytime binocular vision. This combination of the images is known as binocular fusion. Seeing things with both eyes makes the image appear to be brighter, clearer, and to give additional detail than when it is seen only with one eye. If the object is not seen at the same azimuth and elevation with both eyes there can be difficulties in obtaining binocular fusion which can lead to eyestrain and headaches. Poor binocular fusion negates the above-mentioned advantages of using a binocular night vision device. At the present time, it is believed that there is no method of ensuring that any two monocular devices chosen at random would be collimated.
It is thus an object of the invention to provide apparatus for forming a binocular device from two monocular devices.
It is a further object to provide a method of collimating monocular devices for use in a binocular device.
In accordance with an aspect of the invention, apparatus is provided for forming a binocular device from two monocular devices comprising a structure having a pair of mounting regions which define a distance therebetween corresponding to a desired, nominal binocular spacing between two monocular devices, and a pair of fasteners, each of which is for removably securing a respective monocular device to a mounting region.
In accordance with a further aspect of the invention, a method of collimating monocular devices for use in a binocular device is provided, comprising the steps of:
rotating the eyepieces of the monocular devices by the same predetermined amount in the same direction with respect to a fixed reference point on the monocular device;
providing a mounting means having a right mounting position for a monocular device and a left mounting position opposite the right position;
securing the first monocular device to the mounting means at either the right mounting position or the left mounting position in such rotative orientation that if in the right position an object in the center of field of view of the monocular device is located slightly left in azimuth and centered in elevation, and if in the left position an object in the center of field of view is located slightly right in azimuth and centered in elevation; and
securing the second monocular device in the mounting means in the opposite position from the first monocular device in a rotative orientation 180xc2x0 displaced from the rotative orientation of the first monocular device.
Other aspects of the invention will become apparent by reference to the following description and claims.